1. Field of the Invention
The present invention relates to an apparatus and method for calculating a Sum of Absolute Differences (SAD) for motion estimation of a variable block.
The present invention relates to motion compensation used for image data compression, and more particularly, to a method of detecting in parallel a motion vector with respect to a variable block size.
The present invention is derived from a project entitled “Elements and Module for Ubiquitous Terminal [2006-S-006-02]” conducted as an IT R&D program for the Ministry of Information and Communication/Institute for Information and Technology Advancement (Republic of Korea).
2. Discussion of Related Art
H.264/AVC exhibits a higher compression rate than a previous compression standard, and may lower a data transmission rate up to 50% or greater compared with MPEG-4. However, with the use of a new technique developed to achieve a higher compression rate, calculation can be increased up to 16 times greater than MPEG-4.
The basic processing unit of H.264/AVC image compression standard is a macroblock with a block size of 16×16 pixels. Macroblock data is encoded into differential data and a motion vector through intra prediction and inter prediction, and the encoded data are transmitted. Here, the smaller the size of a unit block used for motion estimation becomes, the more accurate the prediction. However, in this case, motion vector data should be encoded per block, and this results in increased encoding processes.
Due to the relationship between the accuracy of prediction and the encoding processes, a method of using an optimal macroblock size among various macroblock sizes has been introduced in H.264/AVC. In MPEG-2, fixed-size macroblocks of 16×16 were used, and in MPEG-4, two types of macroblocks of 16×16 and 8×8 were used. But, in H.264, 7 types of macroblocks are of 16×16 to 4×4 are used.
When various sizes of macroblocks are used in the motion estimation method, the degree of screen compression may be increased, and the amount of calculation is increased as well. In particular, the motion estimation process takes the largest amount of calculation in H.264 encoding calculation, and thus a method that can efficiently process the calculation is required.